i have installed vista and it worked fine for a few days then i was using it and it just shut off and now i carnt turn it on.i have a winfast 7600gt and 2048mb ram. not sure about the psu i have herd that it is a good brand

When you say "shut off", do you mean the computer actually shut down? Do you have any power at all? When you press the power button, does any lights come on, do you hear fans running, etc? If not I would assume it would be the power supply. If you are getting power, I would start taking things out, to see if it will boot- any PCI cards, etc- you need nothing but the necessary items to get it to boot- proc, mem, hard drive, and power connections. Let us know how it goes.

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